There is a type of thermal heads used for thermal recording in various types of printing devices, such as the rewritable printers, the card printers, the video printers, the barcode printers, the label printers, the facsimile machines, and the ticket vending machines. This type of thermal heads heats the recording medium to a predetermined temperature to print information thereon or erase information therefrom. More specifically, a thermal head of this type is designed to selectively apply an electric potential to at least one heat element linearly disposed therein to generate heat. The recording medium reacts with the resulting heat energy. Characters or pictures are thereby printed on the recording medium. Alternatively, characters or pictures are thereby erased from the recording medium.
In a conventional thermal head, the protective layer rubs against the recording medium. The recording medium is, for example, a printing paper. The protective layer is thereby electrostatically charged. When the resulting electrostatic charge accumulation is discharged, this could damage the heat element or the bonding pad portion. There are techniques to prevent such electrostatic discharge damage. One such technique is a method of providing an electrically conductive film on the surface of the protective layer. For example, there is a technique disclosed in the prior art literature to provide an electrically conductive film on the protective film (or protective layer), the pattern of the conductive film being the same as that of the common electrodes or the individual electrodes (see Patent Document 1). There is also a prior art technique to provide an electrically conductive cermet film, thereby producing the resistance to abrasion and the electric conductivity (see Patent Document 2). There is also a prior art technique to cover the protective film with an electrically conductive film and remove the electrically conductive film configured to overlie the heat elements, thereby preventing electrostatic discharge damage and preventing refuse particles from being generated from the electrically conductive film due to this film frictionally sliding against the recording medium. This conductive film is connected to the ground potential via the circuit board by means of patterning (see Patent Document 3). This electrically conductive film is electrically connected to the ground potential of the circuit board by means of patterning (see Patent Document 3).                Patent Document 1 refers to JP5-286154A;        Patent Document 2 refers to JP 10-034990A; and        Patent Document 3 refers to JP 2004-195947A.        